Mosquitoes Prey on Beneficial Barn Owl Nestlings, But Permethrin Can Help

GAINESVILLE, Fla. — Barn owls make their homes in boxes put up by farmers in South Florida. The growers like the owls because they eat rodents that would otherwise munch on their sugarcane, sweet corn and rice.

Researchers with the University of Florida Institute of Food and Agricultural Sciences have found that mosquito bites can contribute to the deaths of the beneficial barn owls. But scientists also found they can use the insecticide permethrin to ward off the mosquitoes that prey on little barn owls – known as “nestlings.”

When UF/IFAS researchers put permethrin inside the nest box, the number of mosquitoes went down – without negatively impacting the little owls. Permethrin is effective at repelling and killing a variety of arthropods, said Caroline Efstathion, a scientist who led the study when she was a Ph.D. student at the UF/IFAS College of Agricultural and Life Sciences (CALS).

“It actually increased their survival rate compared to nestlings in boxes with no insecticide,” said Efstathion, who did her doctoral work at the UF/IFAS Fort Lauderdale Research and Education Center. “This is important because there are several endangered birds whose populations are declining, from botflies and other biting insects. We hope permethrin can be used to benefit these species.”

“The birds benefit from the nest boxes, and farmers benefit from the rodent control,” she said. “We showed that mosquitoes are a factor to consider in the conservation of endangered birds.”

Barn owls, whose populations are declining worldwide because of habitat alterations and the lack of nesting sites, thrive in South Florida because farmers have installed nest boxes for them, according to UF/IFAS research. Growers, especially those who produce sugarcane in the Everglades Agricultural Area (EAA), use barn owls to reduce rodent populations and damage in their crops. The 700,000-acre EAA encompasses an area near Lake Okeechobee.

For the study, scientists attached mosquito traps to boxes where barn owls nested in sugarcane fields, said Nathan Burkett-Cadena, a UF/IFAS assistant professor of entomology, and a co-author on the study. With the traps, researchers caught up to 3,193 mosquitoes in one box one night, suggesting that nestling owls (the young ones) get bitten a lot at night, said Burkett-Cadena, a faculty member at the UF/IFAS Florida Medical Entomology Laboratory in Vero Beach, Florida.

Efstathion, a CALS doctoral alumna studying entomology and nematology, conducted her Ph.D. work under the supervision of UF/IFAS entomology associate professor Bill Kern, another study co-author. The new UF/IFAS study is published in the Journal of Wildlife Diseases.

The mission of the University of Florida Institute of Food and Agricultural Sciences is to develop knowledge relevant to agricultural, human and natural resources and to make that knowledge available to sustain and enhance the quality of human life. With more than a dozen research facilities, 67 county Extension offices, and award-winning students and faculty in the UF College of Agricultural and Life Sciences, UF/IFAS works to bring science-based solutions to the state’s agricultural and natural resources industries, and all Florida residents. Visit the UF/IFAS web site at ifas.ufl.edu and follow us on social media at @UF_IFAS.